Grinding lathe tools

May I put in my ½ pen’oth (In old money where 1/2d was 1” Dia).

I never regrind the indexable tipped tools. I will touch them up with a solid flat diamond file or on a diamond plate, taking care to keep the surface dead flat. I also just touch the finished edge with the diamond to ‘break the kerf’ NB take of no more than 0.001 mm)

Brazed tips I will touch up with the same diamond tools mentioned above. If they become badly chipped I clean them up with a 60 or 80 grit diamond stone cutting wheel which is backed up with a disk of ½” thick alloy to stop it flexing. Here I make no more than 3 passes before I dip in the water tin. I long ago abandoned ‘Green (bauxite) wheels, they made too much dust and mess. Diamond stone cutting wheels are dirt cheap and last a very long time

HSS tools are sharpened or rather honed as for indexed tips on diamonds/carborundem oil stones. If they are too far gone for that or are badly chipped I use my little 'off hand' grinder with 120 grit wheel to re-set them. Two passes then dip in the water and repeat. I finish them by honing as above. Do I use the sides of my wheels? Yes I do, and I also use the front of the wheel taking care to use the whole face to stop groves forming. I also use one of several rests. I have made one set at 10° below the right angle, one at a right angle and one at 2° above the right angle the stone.

To grind a new tool from a new bit of HSS stock by the hand held method can take an hour or more. For this I use the coarse (80 grit) stone to get the general shape. I bought my little grinder in 1970 and have as yet not had to get new wheels for it! This shows just how light my touch is.

The secret is like many other things “Softly softly catchee monkey” slow and easy. You do not need to be a gorillaoid to grind and sharpen lathe (or any other tools for that. A light touch, a good look and a little patience is good.

Rdgs

Dick

How do I know my tools are sharp? I touch them gently on my thumb nail!. Try it you will soon see when they are sharp.

Richard,

I believe the green grit wheels are silicon carbide (carborundum) not aluminium oxide (alumina) - the latter is used in white (and IIRC pink) wheels, but not green.

A light touch is all very well, but try doing that when roughing out a 16mm HSS tool - you'd be there all year!

I generally consider a tool (whether a lathe tool or a woodworking one) sharp if I can't see a noticeable line of light reflected from the edge.

David

Excellent and informative discussion, thanks chaps.